Digital inkjet printing is becoming an increasingly popular method for the production of fine graphic images for advertising, due to its low implementation cost and versatility in comparison with traditional techniques such as lithographic and screen printing. Inkjet printers comprise one or more printheads that include a series of nozzles through which ink is ejected onto a substrate. The printheads are typically provided on a printer carriage that traverses the print width (moves back and forth across the substrate) during the printing process.
Two main ink chemistries are used: inks that dry by solvent evaporation and inks that dry by exposure to ultraviolet radiation. Wide format solvent-based inkjet printers are an economic route into the industry as they are a relatively low cost option compared to the more complex machines employed for UV curing. Solvent-based inkjet printing also has other advantages. As well as the lower cost, the ink films produced are thinner (and therefore flexible) and yield a good quality natural looking image with a gloss finish. Furthermore, it is difficult to achieve very high pigment loadings in UV curable inks due to the high viscosity of the ink: if too much pigment is added, the ink becomes too viscous and cannot be jetted. In contrast, solvent-based inks include a high proportion of solvent and therefore have a lower viscosity, which means that higher pigment loadings can be tolerated. In addition, the printed film produced from solvent-based inkjet inks is formed predominantly of pigment along with comparatively few other solids that are included in the ink. The pigment is therefore largely unobscured, resulting in intense, vivid and vibrant colours and a large colour gamut.
However, there are some limitations to solvent-based inkjet technology. In particular, solvent-based inks may not adhere to certain types of substrate, particularly non-porous substrates such as plastics, and the cured films have poor resistance to solvents.
There therefore exists a need for an alternative inkjet ink and a printing apparatus that is capable of printing the ink.